1. Field of the Invention
This invention relates to electric drive propulsion units for railway cars or the like, and more particularly to the motor-to-drive gear coupling and suspension systems thereof.
2. Description of the Prior Art
Electrified railway cars of the type to which the present invention is applicable are of the parallel drive type and include street cars, transit or subway cars, and heavy commuter cars, to name a few. In such cars, each separate truck is typically provided with its own traction motor(s) and gear box drive arrangement(s). While such trucks may be constructed with their frame stringers either inside or outside the truck wheels, the present trend in the construction of railway cars in North America as well as elsewhere has been toward the use of inside frame trucks. It will be appreciated that this limits the space available for the mounting of the various drive components between the longitudinal frame sections or stringers and thus exacerbates problems relating to the misalignment of drive train shafts and accommodation of relative movement between individual components of the drive system.
It has been known in the prior art to rigidly mount the gear drive unit and the motor output shaft together with the gear box portion of the motor gear box assembly being coupled to the driving wheel axle. Such arrangements, however, have not been entirely satisfactory from the standpoint of operating lifetime and maintenance-free operation, due to the load of motor torque and the weight of the gear box assembly which are imposed on the resilient coupling between the drive gear and the driven axle.
Other propulsion systems of the prior art have avoided problems of a resilient coupling between the drive gear and the axle by solidly coupling the axle drive gear to the axle and providing resilient coupling between the gear box and the traction motor. Such an arrangement is disclosed in U.S. Pat. No. 3,468,389 of James A. Nelson.
Still another arrangement which combines the aforementioned resilient coupling between drive gear and axle with a resilient suspension system for the gear box assembly is disclosed in U.S. Pat. No. 3,841,228 of Walter O. Hall.
Still another system for resiliently mounting a traction drive suspension system is the subject of U.S. Pat. No. 3,877,388 of Walter O. Hall et al.
Such resilient mounting systems include pads, bushings or other elements of a resilient material which are subject to deterioration from the extreme load conditions imposed on them. However, according to the above-cited prior art patents, it has heretofore been considered essential to utilize resilient coupling in the drive train and/or resilient mounting of the drive system components in order to accommodate the relative movement of the various elements with respect to each other which is encountered in normal operation. Such relative movement results from unevenness of track and roadbed and from variations in the drive torque load and may involve vertical, longitudinal and lateral displacement as well as angular misalignment. While such relative movement may be comparatively slight, the forces involved are very substantial in view of the loads which are encountered in normal use.